Added sitemap generation

[johannesberdin]

Big 👍 for your work.

We think it could be helpful to have a basic sitemap so we adapted the code from the RSS feed builder.

User needs to set sitemapView in config.php and a sitemap blade template.

Basic example:

<?xml version="1.0" encoding="UTF-8" ?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  @foreach($sites as $site)
  <url>
    <loc>{{ $siteUrl }}{{ $site }}</loc>
  </url>
  @endforeach
</urlset>

[vidalvasconcelos]

Hey, its very cool!